With the recent increase in the data bandwidth handled by systems, serial interfaces with a speed as high as the gigabit per second (Gbps) level have been put into practice as interfaces between information processing apparatuses, and have become widespread. For example, fibre channel interfaces, serial advanced technology attachment (SATA) interfaces, and the like have become available.
In transmission systems based on high-speed serial interfaces, when the transmission distance is long and if values of a driver during transmission such as an amplitude value and an emphasis value indicating the degree of emphasis in the high-frequency range of the transmission waveform are used with values unchanged from the initial values, the transmission amplitude may be insufficient. Conversely, when the transmission distance is short, the transmission amplitude may be excessive. That is, the installation environment may differ depending on the system used. Therefore, it is preferable to reset the settings of the driver and the like to values that are optimum for the system in terms of the transmission state. Optimum values of the individual parameters are calculated by performing a transmission simulation, impractical calculation of transmission loss, or the like in advance. During inspection before shipment of the devices, the values are actually set in the devices and received waveforms are observed to make sure that no transmission errors occur. Thereafter, the finally determined values are set as fixed values and set in the devices before shipment.    [Patent Document 1] Japanese Laid-open Patent Publication No. 2007-53648